The Hawthorne Studies

In the 1920s, researchers at the Hawthorne Works, a large factory near Chicago, set out to answer a practical question: does better lighting make workers more productive? They increased the lighting for one group of workers while keeping it the same for another group. To their surprise, productivity rose in both groups. [A] Even when the lights were later dimmed, output often continued to improve. [B]

[C] Later experiments at the factory examined rest breaks, working hours, and methods of payment, and again productivity seemed to rise with almost every change. The researchers eventually concluded that the workers were responding not to the specific changes but to the attention they were receiving. [D] This idea — that people change their behavior when they know they are being studied — became known as the Hawthorne effect.

The Hawthorne effect is still discussed in textbooks, and it is one reason that many studies compare two groups that both receive attention from researchers. However, when economists reexamined the original lighting data in 2011, they found much weaker evidence for the effect than had been reported. Some of the improvements may have been due to other factors, such as seasonal patterns in output or changes in which workers took part.